A wide variety of machines for extruding rubber and plastic materials have been in use for many years. In recent years technical developments have made possible the extrusion of a wider range of materials, products of greater size and more intricate cross-sectional configurations, and faster extrusion rates under virtually all circumstances. As a result, increasing numbers of components and parts once fabricated by different methods due to material, tolerance or size limitations are now processed in extrusion lines. While separate or off-line cutting operations were at one time used extensively, such are normally deemed relatively expensive in terms of apparatus and/or labor costs by current standards.
Therefore, extruder lines consist generally of an extruder which produces an endless flow of product and on-line cutting apparatus which severs the product to predetermined lengths. Types of products which are commonly produced include flat goods in the nature of seals or weather stripping and tubular goods such as various types of hosing and tubing. Extruder lines are commonly available which are capable of handling goods which may be from a fraction of an inch in maximum dimension up to 6 inches or greater. The number of cuts per minute and thus the number of pieces by way of production rate per minute may include requirements of from a few cuts per minute to in excess of one thousand cuts per minute.
A great variety of cutting apparatus has been developed for affecting cutting of the endless flow of product emanating from an extruder. Depending upon the material being processed, the product may be either push or pull fed into the proximity of the cutter area of the cutting apparatus at substantially the linear extrusion rate of the extruder. A substantial number of on-line cutters designed over the years mount one or more blades on a rotating flywheel. The blade is set to rotate at a speed to provide the necessary linear length of cut extrusion for the rate at which material is extruded and fed to the cutter. These flywheel cutters operate on a timing basis in that cuts are repeatedly made at each duration of a selected time interval, thus assuming that the exact desired cut length of material will pass the knife cutting point during each time interval.
These flywheel cutters experienced variations in the length of the cut material under operating conditions which could even minutely vary the extruder feed rate. In addition, these cutters are difficult to set up without extensive trial and error correction and require resetting whenever the extrusion rate is altered. In many instances these cutters became known as maintenance-prone for a variety of reasons.
More recently rotating knife cutters have been developed which employ some different but some substantially identical features. These cutters employ a clutch/brake system which, upon a signal, rapidly rotates the knife through one revolution, then stops and repeats on repetitions of the signal. Rather than operating on a time basis between signals, recent rotating knife cutters employ control devices which physically measure each predetermined length of material and then produce a knife activating signal. Such control devices may employ measuring wheels, mechanical trips or electric eyes to provide accurate measurement of each length of material. While these rotating knife cutters generally achieve improved accuracy and operating speeds in relation to flywheel cutters, they are not without attendant disadvantages. For example, the clutch/brakes and controls need to be highly accurate and therefore sophisticated which makes the cutter initially relatively expensive as well as more complex and costly to maintain and repair. Thus, the various types of cutting apparatus currently being employed are commonly subject to some disadvantages in terms of operation, cost considerations, or both.